Abstract
We study non-linear absorption of intense monochromatic light through a dense natural rubidium (Rb) vapour. We measure transmission through a 10 cm long heated vapour cell for atom densities up to 3 × 1019 m−3 and saturation parameters up to 104, for linear and circular polarisation, close to resonance on the 87Rb D2 F = 1 → F′ = 0, 1, 2 transition. The strong absorption at low intensity is frustrated by an interplay of optical non-linearities (saturation and optical pumping) and non-linear effects due to the high atom density (collisional broadening and collisional depumping). To understand the results of the transmission measurements, we developed a model that incorporates these non-linear effects into the optical absorption. The model takes into account the absolute line strengths of all transitions from both hyperfine levels of the ground state of both isotopes of naturally abundant Rb. Doppler and collisional broadening are included in the Voigt profiles for the resonances. We show the effect of each of the non-linear processes on the calculation results of the model, and from comparison with experiment we conclude that all non-linear effects are necessary for a quantitative agreement.
Highlights
The study of optical properties of dense atomic vapours has resulted in the observation of fascinating non-linear effects on the propagation of light through such media [1]
We study non-linear absorption of intense monochromatic light through a dense natural rubidium (Rb) vapour
The principles of the model are applicable to any transition in an atomic vapour
Summary
The study of optical properties of dense atomic vapours has resulted in the observation of fascinating non-linear effects on the propagation of light through such media [1]. For speci c ranges in intensity, atom density and detuning, these properties have been reported in earlier work: absorption has been studied at low laser intensities for high vapour densities [24, 28, 29], absorption with optical pumping at medium intensities [30,31,32,33], and absorption and refraction at high intensity and high atom density for large detunings [26, 34] We capture these properties in a comprehensive model applicable over the whole range of detunings, saturation parameters and atomic densities. We show the in uence of each of the effects on the resulting transmission curve and show all effects are necessary to achieve quantitative agreement with the experimental results
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